It is known that there are naturally occurring opiate-like peptides (endorphins) which appear to function as neurotransmitters and neuromodulators within the central nervous system. The major goal of this project is to study the possible neurobiologic role of endorphins in human behavior and psychiatric illness. The Unit has tested the behavioral effects of the narcotic antagonist, naloxone, and of beta-endorphin in affectively ill and schizophrenic patients. A sensitive radioreceptor assay to determine opioid activity in human CSF and plasma has been developed. This assay is currently being used to study the physiologic role of endorphins in man and possible disturbances in psychiatric patients.